Hydraulic power systems utilize hydraulic pressure for controlling power units. For safety and other considerations, these systems often use a pressure switch to provide an electrical signal indicating that a preset pressure has been met and a separate pressure regulator to protect the system against being over-pressurized. There also exists combined pressure regulator and pressure switches which provide both pressure signal and protection in a single unit.
The use of separate pressure switches and pressure regulators creates the problems of a user having to make two separate pressure adjustments--one adjustment for the pressure switch, and a separate adjustment for the pressure regulator. This can be difficult since the two are somewhat interactive. If the pressure regulator is set too low, then the pressure switch cannot be set. If the pressure regulator is set too high to avoid this situation, then there is no protection against over-pressurization during the setup operation. Likewise, if the pressure switch is set too low, then the power unit can shut off before the pressure regulator can be set. Thus, the setup operation, in using separate pressure switch and pressure regulators, is especially difficult when operating pressure of the system is constantly changing, requiring repeated resets.
Other problems exist with combined pressure regulators and pressure switches. These devices typically route the return hydraulic flow from the pressure regulator through an orifice, thus creating a back pressure to trigger a pressure switch. This eliminates the need for two separate pressure settings. However, because this design utilizes an orifice, there is the potential for malfunction due to contamination clogging the orifice. Also, operation can be sluggish due to oil viscosity during cold weather operation, or malfunction in hot weather operation. Because the pressure switch is triggered by the return oil from the pressure regulator, the switch can prematurely trigger if the hydraulic seat in the pressure regulator becomes worn.
The present invention is directed to solving one or more of the problems discussed above in a novel and simple manner.